1. Field of the Invention
This invention relates to certain carboxylates as activator-stabilizers in heat developable photographic elements, compositions and processes. In one aspect the invention relates to heat-developable photographic elements containing the described thiazolinium compounds. In another aspect it relates to photographic compositions such as photographic silver halide emulsions containing the described thiazolinium compounds. A further aspect relates to a method of developing and stabilizing an image in a heat-developable photographic material with the described thiazolinium compounds by heating the photographic material.
1. Description of the State of the Art
Heat-developable photographic materials are known. These materials are designed for so-called dry processing with heat. These materials are described, for example, in U.S. Pat. No. 3,301,678 of Humphlett, Johnson and Haist, issued Jan. 31, 1967; British Pat. No. 1,161,777 published Aug. 20, 1969; U.S. Pat. No. 3,152,904 of Sorensen et al, issued Oct. 13, 1964; British Pat. No. 1,131,108 published Oct. 23, 1968; U.S. Pat. No. 3,392,020 of Yutzy et al, issued July 9, 1968; German Pat. No. 888,045 published Aug. 27, 1953; British Pat. No. 930,572 published July 3, 1963; and U.S. Pat. No. 3,220,846 of Tinker and Sagura, issued Nov. 30, 1965.
Stabilizer precursors are also known in photographic materials for processing with heat. These are described, for example, in U.S. Pat. No. 3,301,678 of Humphlett, Johnson and Haist, issued Jan. 31, 1967. It has been the practice to incorporate a development activator or alkali-release agent which is different from the developing agent or developing agent precursor or stabilizer precursor in such photographic materials. This is described, for instance, in U.S. Pat. No. 3,041, 170 of Haist and King, issued June 26, 1962 and Belgian Pat. No. 709,967 issued Feb. 29, 1968. These photographic materials did not eliminate the need for a separate development activator and alkali-release agent.
It is further known that certain bis-isothiuronium compounds having an intermediate ureylene or ether moiety between the isothiuronium moieties can be development activators and image stabilizers in photographic materials for processing with heat. This is described in U.S. Pat. No. 3,669,670 of Haist and Humphlett, issued June 13, 1972.
Photothermographic materials incorporating isothiuronium stabilizer precursors have required higher processing temperatures than desired. They also have required larger concentrations of processing chemicals than desired and often are confined to use with photographic materials which are relatively low speed, smaller grain silver chloride and silver chlorobromide photographic materials. In many cases they also have resulted in obnoxious odors upon heat processing.
Heterocyclic thione and tautomeric thiol compounds have been used for different purposes in photographic materials. For example, certain heterocyclic sulfur compounds or their tautomeric thiols have been used in photographic silver halide materials for processing with heat. This is described, for example, in German OLS 2,162,714 published July 6, 1972. These compounds, however, have not provided the desired image with reduced processing temperatures or have not provided desired activation of the incorporated developing agent in the heat-developable photographic material.
Heterocyclic compounds such as thiazoles and thiazolines have been employed in photographic materials for other purposes, such as fixers, as described in U.S. Pat. No. 3,189,453 of Hertz and Kalenda, issued June 15, 1965.
There has been a continuing need to provide heat-developable and heat-stabilizable photographic silver halide materials and processes which enable use of lower processing temperatures, reduced concentrations of processing materials and which enable use of a wider range of silver halide photographic materials without the production of obnoxious odors upon processing with heat.